Vitamin K is one of those substances which from time to time appear in medicine suddenly, entering the field with a fine flourish and performing in such a spectacular fashion that for a time they come to occupy the center of the stage.

Vitamin K was found unobstrusively. The original papers describing its usefulness in the treatment of a scurvy-like disease of chicks were published between 1929 and 1934. As so often happens, several years lapsed before clinicians realized the possible implications for human beings of a deficiency disease in chicks characterized by easy bleeding and relievable by a fat-soluble vitamin occurring in hog liver, hemp seed and certain cereals and vegetables. But in 1938 three independent papers drew attention to the fact that what was termed vitamin K had definite usefulness in overcoming the bleeding tendency encountered in cases of obstructive jaundice. Subsequently there has sprouted up a voluminous